1. Field of the Invention
This invention relates generally to surveillance systems used in the prevention of shoplifting, and in particular, to a surveillance system used to prevent shoplifting by placing items on the lower tray of a shopping cart.
2. Description of Related Art
Retail stores suffer millions of dollars of losses each year as a result of the theft of products occurring when customers intentionally or accidentally conceal items on the lower tray of their shopping carts. Retail stores are particularly vulnerable to this problem because store cashiers cannot observe the lower tray of the shopping cart from a store cashier's normal position. Although store cashiers can inspect the contents of the lower tray of a shopping cart by leaning over the checkout counter, this motion poses an inconvenience to the cashier. Furthermore, customers may consider as rude this potentially mistrustful display. Thus, retail stores having multiple cashiers and multiple checkout aisles with multiple checkout counters need a system which would allow the inspection of the lower tray of a shopping cart without needlessly inconveniencing the store cashier, or unintentionally offending the customer.
Several systems have been developed to alert a store cashier to the presence of a parcel positioned on the lower tray of a shopping cart as that cart passes through the checkout aisle. U.S. Pat. No. 4,327,819 issued to Coutta on May 4, 1982 for OBJECT DETECTION SYSTEM FOR A SHOPPING CART, U.S. Pat. No. 4,725,822 issued to Hooley on Feb. 1, 1988 for SHOPPING CART WITH LOWER TRAY SIGNALING DEVICE, and U.S. Pat. No. 4,736,098 issued to Rehrig on Apr. 5, 1988 for SIGNALING METHOD AND APPARATUS FOR A CONVENTIONAL SHOPPING CART each disclose systems whereby a combination of a light transmitter, light detector and a reflector mounted on the lower tray of a shopping cart act in concert to detect the presence of unpaid for articles on the lower tray of a shopping cart passing through a checkout aisle. Unique to the systems described in the these patents is the use of springs which bias the lower tray towards one position so that the increased weight of parcels placed on the lower tray depresses the tray, bringing the reflector into the path of the beam of light emitting from the transmitter. Still, the need for the retrofitting of the shopping carts with reflectors limits the effectiveness of this system.
The invention disclosed in U.S. Pat. No. 4,548,295 issued to Lundgren et al. on Oct. 22, 1985 for COUNTER SYSTEM illustrates one mechanical approach to the problem of unpaid-for products residing on the lower tray of a shopping cart. Lundgren et al. teaches the use of a receiving section constructed as part of the checkout counter which physically removes any articles present on the lower tray of the shopping cart as the cart passes through the disclosed system. The Lundgren system, however, is incapable of distinguishing between unpaid-for articles and non-store goods, like a purse or handbag.
Similarly, the applicants in U.S. Pat. No. 4,723,118 issued to Stillwater et al. on Feb. 2, 1988 for MAGNETIC DETECTION SYSTEM FOR ITEMS ON THE LOWER TRAY OF A SHOPPING CART employ a non-optical approach in identifying unpaid-for items on the bottom tray of a shopping cart. Stillwater et al. describe a magnetic detection system for unpaid-for items on the lower tray of a shopping cart. Like the invention revealed in the Coutta patent, the system disclosed by Stillwater et al. utilizes a spring biased lower tray. But, instead of using an optical combination of light source, light detector and light reflector, the invention disclosed in the Stillwater patent includes a magnet attached to the shopping cart lower tray, so that a change in the position of the tray resulting from items resting thereon, causes the displacement of the magnet attached to the tray and a corresponding change in the magnetic field. Nevertheless, like the preceding inventions, the system described by Stillwater et al. requires retrofitting existing shopping carts. Furthermore, the Stillwater et al. invention cannot distinguish between unpaid-for products and non-store articles.
In recent years, inventions disclosed by several patents have implemented lower tray detection systems using light transmitters and detectors positioned on either side of the checkout aisle. As a result, this type of system eliminates at least the retrofitting requirement of prior systems. In particular, U.S. Pat. No. 5,485,006 issued to Allen et al. on Jan. 16, 1996 for PRODUCT DETECTION SYSTEM FOR SHOPPING CARTS, U.S. Pat. No. 5,495,102 issued to Fine on Feb. 17, 1996 for SHOPPING CART MONITORING SYSTEM, and U.S. Pat. No. 5,610,584 issued to Schrade for DETECTION OF GOODS ON THE BOTTOM RACK OF A CART each include systems having infrared lights sources and detectors positioned across the width of a checkout aisle.
Significantly, these systems only alert the cashier to the presence of an object, not necessarily an unpaid-for product, on the lower tray of the shopping cart. None allow the cashier to visually inspect the contents of the lower tray. Although the Allen patent teaches the use of a video camera in a detection system, the Allen patent specifically limits the utility of the camera to a method for recording evidence of an object detected on the lower tray of a shopping cart. Thus, neither the camera disclosed in the Allen patent nor the inventions recited in the Fine and Schrade patents allow the cashier to personally observe and inspect the lower tray's contents.